The present invention relates to an electronic device and a method for fabricating the electronic device, more specifically, an electronic device having electronic circuit elements hermetic sealed and a method for fabricating the electronic device.
As electronic circuit elements are increasingly highly integrated by the progress of the recent micronization technology, drastic increase of the processing speed and the cost reduction have been realized.
Semiconductor devices for industrial apparatuses, and cars are considered to be used in severe environments, as of high temperature, high humidity, etc. The semiconductor chips must be sealed in a package having high sealing performance.
SAW (Surface Acoustic Wave) devices used as the radio-frequency of portable telephones, etc. must be sealed hermetically so as to protect the comb electrode pairs.
As a method for sealing semiconductor chips, etc. in a package so as to shut the semiconductor chips, etc. off from the outside atmosphere, a method for mounting the semiconductor chips, etc. in a package to seal the semiconductor chips hermetically with a metal cover of stainless or others placed on the package is known. The cover is secured to the package with the semiconductor chips, etc. mounted on with soldering, welding or others. Outside connection terminals led out of the inside of the package are provided on the package, and the signal lines, etc. of the semiconductor chips, etc. mounted on the package are connected to the outside connection terminal with bonding wires, etc.
Semiconductor chips, etc. with electronic circuit elements formed on are sealed in a package having high sealing performance, whereby an electronic device which can stand severe environmental conditions can be provided.
[Patent Reference 1]
Specification of Japanese Patent Application Unexamined Publication No. 2004-214469
[Patent Reference 2]
Specification of Japanese Patent Application Unexamined Publication No. Hei 10-189819
[Patent Reference 3]
Specification of Japanese Patent Application Unexamined Publication No. 2003-110402
[Patent Reference 4]
Specification of Japanese Patent Application Unexamined Publication No. 2002-110869
However, in the conventional methods, the metal cover, the package of ceramics or others are expensive, which increases the cost. The cover and the package itself are relatively large, which might be a barrier to smaller-sizing the electronic device.
Furthermore, the above-described patent references have the following problem.
Patent Reference 1 discloses the technique that the electrodes on electronic circuit element (SAW chip) and electrodes on a package substrate are bonded with metal, and the outer peripheries of the device formed regions are bonded with an intermetallic compound, whereby the comb electrodes of the SAW chips are shut off from the outside so as to protect the device formed regions including the comb electrodes. However, this structure has a problem that stresses are applied to the SAW chips due to high bonding temperatures of the intermetallic compound.
Patent Reference 2 discloses the technique that when integrated circuit chips are mounted on an insulation substrate by flip chip method, barrier bumps are provided at the outer peripheries of conducting bumps, whereby the circuit formed surfaces and the electrodes, etc. of the chips are shut off from the outside for protection. However, this structure has a problem that the barrier bumps (of solder, gold or others) are melted to be bonded, and the integrated circuit chips are susceptible to stresses of the thermal expansion coefficient. The barrier bumps are melted, and might flow out. It is difficult to control the thickness of the barrier bumps.
Patent Reference 3 discloses the technique of the surface acoustic wave device that surface acoustic wave chip is flip flop bonded to a package substrate, and then the surface acoustic wave chips are covered with a glass material of low melting point to thereby seal the interior hermetically. However, this structure has a problem that the inside chips are exposed to the high glass melting temperatures and are damaged. It is also a problem that to ensure sufficient seal strength, a thickness which is several times a thickness required for the sealing with a metal cover or others is required.
Patent Reference 4 discloses the technique that semiconductor chips mounted by flip chip bonding are hermetic sealed by using a resin plate and a metal bellows spring. This technique has a problem that the structure is complicated, and the material of the metal spring, etc. is expensive.